System and methods for positioning bone cut guide

ABSTRACT

Examples of an orthopedic surgical device for use in operating on a target bone and methods for operating a system for use in orthopedic surgery on a bone are generally described herein. An orthopedic surgical device can include an primary positioning block, and a secondary positioning component removably coupled to the primary positioning block. The secondary positioning component can be configured to: engage a prepared engagement feature machined into the target bone, and guide the primary positioning block to a predetermined position on a target bone. The orthopedic surgical device can include a first cutting block configured to: removably couple to the primary positioning block, and guide a cutting tool to cut the target bone.

CLAIM OF PRIORITY

This patent application is a continuation of U.S. patent applicationSer. No. 15/428,357, titled “System and Methods for Positioning Bone CutGuide,” filed on Feb. 9, 2017, which is a continuation of U.S. patentapplication Ser. No. 14/634,422, titled “System and Methods forPositioning Bone Cut Guide,” filed on Feb. 27, 2015, which claims thebenefit of priority of U.S. Provisional Patent Application No.61/946,428, titled “System and Methods for Positioning Bone Cut Guide,”filed on Feb. 28, 2014, and further claims the benefit of priority ofU.S. Provisional Patent Application No. 62/119,001, titled “System andMethods for Positioning Bone Cut Guide,” filed on Feb. 24, 2015, each ofwhich is hereby incorporated by reference herein in its entirety.

This patent application claims the benefit of priority of U.S.Provisional Patent Application Ser. No. 62/119,901, titled “System andMethods for Positioning Bone Cut Guide,” filed on Feb. 24, 2015, whichis hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

This document relates generally to computer-aided orthopedic surgery,and more specifically to systems and methods for positioning a cut guideto a target bone and for altering the target bone using the cut guide.

BACKGROUND

The use of computers, robotics, and imaging to aid orthopedic surgery iswell known in the art. There has been a great deal of study anddevelopment of computer-aided navigation and robotics systems used toguide surgical procedures. For example, a precision freehand sculptor(PFS) employs a robotic surgery system to assist the surgeon inaccurately cutting a bone into a desired shape. In interventions such astotal hip replacement, computer-aided surgery techniques have been usedto improve the accuracy, reliability of the surgery. Orthopedic surgeryguided by images has also been found useful in preplanning and guidingthe correct anatomical position of displaced bone fragments infractures, allowing a good fixation by osteosynthesis.

A cut guide can be used in an orthopedic surgery to assist a surgeon incutting or modifying some portions of a target bone. For example, injoint replacement surgeries such as total hip replacement (THR) or totalknee replacement (TKR), a cut guide can be temporarily attached to thetarget bone such as a femur or a tibia. An orthopedic surgical cuttingtool can be used together with the cut guide to allow the surgeon toselectively cut portions of the ends of the target bone and replacedwith endoprosthetic implants. Positioning a cut guide for use inpreparing the target bone can be a time consuming and complicatedprocess, which is critical to positive outcomes for the patient.

SUMMARY

Quick and reliable positioning of a cut guide can be crucial to theoutcome of orthopedic surgeries such as prosthesis implantation. Injoint replacement surgeries, for example, portions of the articulationtissues of a target bone, such as acetabulum, a femur, or a tibia, needto be resected and altered to allow an implant to be securely positionedonto the target bone. A cut guide positioned on the target bone can beused to guide a cutting saw to resect the target bone to a desiredshape. Proper positioning of the cut guide on the bone can improve theaccuracy of the bone resection and reduce procedure time. On thecontrary, improper positioning of the cut guide can result inundesirable cutting surfaces on the target bone, which can further causeimpingement, increased rates of implant dislocation, wear and failure ofthe implant, among many other complications. The procedure time can alsobe lengthened due to the requirement of modifying the undesirablecutting shape.

Positioning of cut guide onto a target bone usually requires a surgeonto mentally map and compare the shape, orientation, and relativepositions of the implant and the target bones. This method can bedifficult to operate and can suffer from lack of reliability andcertainty. Determining and visualizing the correct positions andorientations of the prosthesis with respect to the target bone can bepractically difficult. Computer-aided tools can be used to assist thesurgeon in positioning the cut guide relative to the bone. However,often the computer-assistance is limited to intraoperative navigation oftraditional cutting jigs. The designs of these jigs, the tools to alignthem, and the implants that they support are all compromises meant toserve a general population. Other systems uses computers to analyzepatient specific images used to design patient-conforminginstrumentation and sometimes even implants specific to the patient.However, these images either use ionizing radiation (e.g. computedtomography images) or are prone to error or gaps in tissuedifferentiation (e.g. magnetic resonance imaging). Therefore, thepresent inventors have recognized that there remains a considerable needfor systems and methods that can assist the surgeon in reliablypositioning a cut guide onto the target bone with improved accuracy,speed, and consistency, while still allowing for some customization forpatient specific differences.

Various embodiments described herein can, among other things, helpimprove the efficacy and the reliability in positioning a cut guide ontoa target bone to alter a portion of the target bone. For example, anorthopedic surgical device can comprise a primary positioning block. Theorthopedic surgical device can comprise a secondary positioningcomponent removably coupled to the primary positioning block, thesecondary positioning component configured to: engage a preparedengagement feature machined into the target bone, and guide the primarypositioning block to a predetermined position on a target bone. Theorthopedic surgical device can comprise a first cutting block configuredto: removably couple to the primary positioning block, and guide acutting tool to cut the target bone.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are illustrated by way of example in the figures ofthe accompanying drawings. Such embodiments are demonstrative and notintended to be exhaustive or exclusive embodiments of the presentsubject matter.

FIGS. 1A-B illustrate generally prepared engagement features, inaccordance with some examples.

FIG. 2 illustrates generally an anterior distal positioning fixture inaccordance with some examples.

FIGS. 3A-D illustrate generally distal cutting block systems inaccordance with some examples.

FIGS. 4A-B illustrate generally a universal adapter and a 4-in-1 cuttingblock in accordance with some examples.

FIGS. 5A-B illustrate generally a tibial cutting block in accordancewith some examples.

FIGS. 6A-B illustrate generally a properly placed femoral implant inaccordance with some examples.

FIG. 7 illustrates generally improperly placed femoral implants inaccordance with some examples.

FIG. 8 illustrates generally a tibial plate trial and navigationpositioner in accordance with some examples.

FIG. 9 is a block diagram that illustrates an example of a computersystem within which instructions for causing the computer system toperform bone cut positioning can be executed in accordance with someexamples.

FIGS. 10-11 are flowcharts showing a method for operating a system foruse in orthopedic surgery on a bone in accordance with some examples.

DETAILED DESCRIPTION

Total knee replacement surgery requires several precise cuts to be madein the femur and tibia in order for the chosen implant to fit correctlyand to restore the geometry and kinematics of a natural healthy knee. Toperform these steps, in both conventional (manual method) and ComputerAided Surgery (CAS) total knee replacement, a series of guide blocks areused that provide a drill or cutting guide to assist the surgeon toperform the steps required to prepare the femur and tibia for receivingthe implant.

The conventional manual instrumented method used to prepare the femurfor a knee replacement implant, outlined below as an example, generallyincludes fastening a distal cutting guide block on the femur, generallylocated by an intramedullary pin (IM rod) or screw inserted into thedistal end of the femur and locating the distal guide block in thedesired position, such position providing correct implant varus-valgusand transverse rotational angle about the IM rod and proper amount ofdistal resection; aligning a distal cutting guide, whether beingintegral with the guide block or a separate element fastenable thereto,in a predetermined location relative to the distal guide block referenceposition and inserting locating pins through the distal cutting guideand into the femoral condyles to fasten the cutting guide in place onthe anterior surface; making the distal cut to resect the predeterminedamount of bone from the distal end of the condyles; positioning a secondfemoral implant sizing guide (the femoral sizer) freely on the newly cutdistal surface of the femur and ensuring that the anticipated resectionlevel for the anterior cut, the anterior-posterior adjustment(referencing off either the existing posterior condyle or the anteriorfemur) for correct implant sizing, and that the rotational alignment andmedial-lateral position of the positioning block are all correct beforefixing the 4-in-1 cutting guide block in place with pins, drilling theimplant peg holes; and performing the anterior and posterior cuts, andsubsequently make the anterior-posterior chamfer and notch cuts. Notethat adjusting rotation of the implant in the sagittal plane isgenerally not possible with the IM rod based instruments typically inuse today. Thus, a femoral implant's position in knee extension isnormally set parallel to the IM rod axis.

The steps required to prepare the tibia are less involved. Generally,they include: aligning the mechanical axis of the tibia; obtainingproper rotational (varus-valgus) alignment of the guide block, andfastening it in place to the anterior surface of the proximal end of thetibia; adjusting the vertical and angular position of the tibial guideblock to ensure that the desired posterior slope and level of tibialresection are provided; inserting location pins using the guide block tofix its position on the tibia; removing the guide block and replacing itwith a tibial resection cutting guide that is retained in place with thelocation pins; and resecting the chosen amount of tibial bone. Note thatthe final position of the tibial plate implant is not determined by thisstep, only the planar surface on which it will rest. Anterior-posterior(AP), medial-lateral (ML), and rotational positioning of the tibialplate implant are subsequently determined by the surgeon's judgment asto its best fitting location on the resected tibia after the femoralimplant has been located and fixed to the resected femur.

The above described surgical procedure remains generally similar whethertraditional or computer assisted surgery is being performed. A CASsystem can employ passive or active trackable elements affixed tosurgical tools and patient bone references, to permit the determinationof position and orientation of the these objects in three-dimensionalspace. In certain types of CAS, preoperatively taken images or computergenerated models created from preoperative patient scans, can be used toprovide accurate patient specific anatomical information. The images ormodels can be used to registered or calibrate real-time position of thesame patient's anatomical elements. This can permit subsequent trackingof the patient's anatomical elements and display of these anatomicalelements relative to the surgical tools used during the surgery.

The use of a cutting/drill-positioning block having aposition-identifying member, such as tracker assemblies, fastenablethereto and trackable by a camera based CAS system, for example, can beused in total knee replacement surgery. While such tracked femoralpositioning guide blocks can provide significant advantages overtraditional non-CAS instruments, the use of the CAS often leads tolonger surgical times.

As discussed above, total knee replacement procedures can include thesame step-wise method of creating the necessary cuts on the femur inorder to resect enough bone to permit the installation of the femoralimplant. In conventional, or non-computer assisted, total kneereplacement surgery, a distal cutting block is positioned and aligned bythe surgeon and pinned in place on the anterior surface of the femursuch that the cutting slot is aligned in the correct location for thedistal cut. In CAS total knee replacement, the CAS navigation locatesthe distal pin drill guide position on the femur to accurately createthe pin holes into which locating pins are inserted and employed toeventually fix the distal cutting guide. Generally, the distaldrill/cutting guide member comprises part of an assembly, including ananterior guiding platform, that is fixed relative to the femur and onwhich the drill/cutting guide is displaceable proximally by a selected,measurable amount to locate the drill/cutting guide in a desiredposition relative to the anterior guiding platform and thereforerelative to the distal end of the femur. A tracked guide block can beintramedullarly fastened to the femur, and the anterior guiding platformcan engage with the tracked guide block. Depending on the type ofimplant being used, and once aligned with the most distal femoralcondyle, the drill/cutting guide can be proximally displaced from thenormal joint line on the fixed anterior guiding platform by a selectedamount, corresponding to the amount of bone to be resected for theparticular implant being used.

The use of CAS can improve the location of implant cutting guides, andby integrated reference, the implant location on the bone but generally,the use of CAS in previous procedures has not changed the basic methodand sequence of performing the bone preparation.

Recently, an alternative CAS system that employs a pre-operativescanning procedure, typically a CT or a MRI, has been successfullydemonstrated. The system provides shape based recognition of the boneand, by planning the desired implant location, is able to provide afabricated, patient-specific cutting jig and a patient-specific implantdevice whose components can be aligned and altered by the physicianprior to manufacturing, according to the specific patient's requirementsand the physician's preference.

A primary feature of this method is the use of pre-procedure imaging ofthe involved joint. The system software, typically provided as a serviceto the physician, calculates the geometrical information on the damagedbone, captured in CT or another suitable imaging format, and convertsthis information into a three-dimensional (3D) model of the bonesurfaces. The converted 3D model includes information on correspondingbone dimensions. The surgeon, using the CAS, determines a femoralmechanical axis (FMA), femoral mechanical center (FMC), femoralanatomical axis (FAA) and tibial mechanical axis (TMA), and decides howand where the implant components should be placed on the bones of theparticular patient. Once the planning is complete, the system softwareprepares and provides a computer file to direct rapid productionmachines, such as a computer numerical control (CNC) machine, a 3Dprinter machine, etc., to fabricate a patient specific, disposablecutting jig or a cutting guide device. The cutting jig and implantdevice can include a surface profile that matches the patient's bonesurfaces in vivo, as predicted by the pre-procedure imaging scan, andcan cause a specific fit of the cutting jig to only one position on thepatient's knee.

Referencing to the geometry of the cutting jig surface profile, guidingholes for drilling and inspection, a slot feature for a sawing process,and bushing features for reaming and drilling can be fabricated into thecutting jig. During surgery, the patient specific cutting jig is fittedonto the predetermined location on the bone to guide critical cuts andshaping of the bone, such as drilling, reaming, sawing, etc., thusensuring the surgeon's pre-determined and desired location of theimplant on the patient's knee.

The above described CAS system uses a computer-aided calibration processthat matches the surface of the cutting jig or implant device to thebone surface(s). Because the cutting jig or implant device is fabricatedusing CT scan image data, there is no need for use of a registrationprocess, tracking systems or robotic systems in the operating room. TheCAS system thus is designed to work in conjunction with manual standardTKA instrumentation and the cutting jig or implant device can provide areduction in surgical time. However, the CAS system above requires theadditional expense of the pre-procedure imaging scan as well as the timeand cost for physician review, fabrication, sterilization, packaging anddelivery of the patient specific cutting jig to the operating room.Additionally, the patient specific cutting jig is only suitable for thedistal femoral cut and tibial cut. The 4-in-1 cutting block must stillbe placed for those cuts after the distal cut has been made. While theabove CAS system can eliminate the use of the IM rod, during surgery, ithas been found that the patient specific instrumentation (e.g., cuttingjig) often does not fit well with the patient's anatomy, revealing alimitation of the accuracy of pre-procedure imaging technique.Adjustments to the patient's anatomy then must be made to ensure properfitting, and this introduces the possibility of implant positioningerrors.

The previously described systems used in total knee replacement surgeryare still lacking in capability, accuracy, and efficiency of timelyplacement.

In an example, a computer controlled surgical instrument can be used incombination with an anatomical navigation system to place, size andlocate specific machined areas onto the bone that will thenunambiguously mate with size specific, non-patient specific,instrumentation. Such equipment can include, for example, the NAVIO®Surgical System from Blue Belt Technologies, RIO robotic arm interactiveorthopedic system from Mako Surgical, daVinci Surgical System fromIntuitive Surgical, and other similar systems. The NAVIO® system can beused effectively because its navigation component does not requirepre-imaging of the patient and instead uses a navigated stylus todetermine actual patient anatomic features in conjunction with fixedbone landmarks such as the femur and tibia. Systems and methods to usethe NAVIO® system are described in U.S. Pat. No. 6,757,582, titled“Methods and Systems to Control a Shaping Tool” to Brisson, et.al, whichis hereby incorporated by reference herein in its entirety.

In an example, a database of implant sizes is contained in CASnavigational software. A surgeon, having fully mapped all of the keyanatomical landmarks, can use the CAS system, in the example of a totalor partial knee replacement, to calculate a femoral mechanical axis(FMA), femoral mechanical center (FMC), femoral anatomical axis (FAA)and tibial mechanical axis (TMA). With this compiled data, which isspecific to the particular patient, the surgeon can use the planningaspect of the CAS software to position the articulating surface of theimplants in virtual space and confirm, through range of motion of theactual joint, that the implant selection and positioning of thearticulating surfaces is correct. Systems and methods to use a CASsystem are described in U.S. Provisional Patent Application Ser. No.61/948,102, titled “Computer-aided Prosthesis Alignment,” filed on Mar.5, 2014, which is hereby incorporated by reference herein in itsentirety.

At this point in the procedure, a typical CAS system would require theuse of cutting guides and instruments that are capable of interactingwith the CAS system, in order to be properly placed in preparation ofmaking the final bone cuts. Alternatively, the MAKO system uses a robotarm to hold the cutting blocks in place, in proper relation to the boneabout to be cut. In either case, once the planning step has finished,the next step for the surgeon is to fix the cutting guides in place,their position determined by the location of the articulating surfaces,relating them to the selected implant backside surface geometry,confirming the required bone resection for the particular implant sizeand then performing the bone cuts, a step that when completed, does notallow for any subsequent change in implant position, even if it isincorrect, due to poor or inadequate planning by the physician.

In an example, the system described herein can improve the previouslydescribed systems for performing the surgery, and can allow for moreinteraction and confirmatory steps by the physician to help assureproper placement of the implant. For example, after virtual placement ofthe implant in the CAS system, instead of going directly to thepositioning of the navigated cutting blocks, a system can use anavigated, controlled instrument (burr) of the NAVIO® system to place aseries of shallow burred areas (e.g., zones or engagement features) atspecific locations on the bone that can provide for the specificlocation of the provided instruments on the bone, without the need forthe instruments themselves to be navigated. Along with the implantdatabase that is part of the CAS system, the database also can includeadditional information that relates specific locations on the backsideof the implant with articulating surfaces. The combination of thissystem and additional implant data can allow the surgeon to makeconfirmatory judgment of the final implant position before irreversiblebone resection has occurred. In another example, the system can allowfor all of the bone cuts to be made using the combination of thenavigated cutting zones and the generic instruments. This combinationallows the CAS system to create a patient specific placement of theimplants without the need for pre-imaging or the need for expensive,navigation capable instruments or expensive robotic arms. U.S.Provisional Patent Application Ser. No. 61/946,428, titled “System andMethods for Positioning Bone Cut Guide,” filed on Feb. 28, 2014, ishereby incorporated by reference herein in its entirety.

A method for operating on a target bone can include using a CAS systemto determine a femoral mechanical axis (FMA), femoral mechanical center(FMC), femoral anatomical axis (FAA) and tibial mechanical axis (TMA)with typical fixed bone navigation trackers/markers and navigationmethods. A navigated stylus can be used to record actual (patientspecific) bone and articular surfaces such as the position, width orshape of the posterior condyles, width or shape of the distal condyle,width or position of the trochlear groove and sulcus on the anteriorfemur, width, slope, relative depth of the tibial plateau or position orshape of any eburnated bone on the tibial plateau or femoral condyle, or“Whiteside's line”. An implant can be virtually placed onto the bone andfitted for best size match, desired extension and flexion gap,varus-valgus alignment, distal position on the femur, proximal positionon the tibia, matching of posterior, distal and sulcus articularsurfaces with those of the femoral implant, rotation in the sagittalplane of the femoral implant or posterior slope of the tibial implant,or internal-external rotation of the implants.

In an example, since the implant geometry, specifically the femoral andpolyethylene insert implant articulating surfaces, can be known to theCAS system via a database, the ML, AP, and rotation of the tibialcomponents (tibial plate and polyethylene insert) can be aligned on theresected tibia to a best fit position relative to the femoral implant.This can avoid creating a mismatch of the femoral and tibial componentsduring ambulation.

After the virtual implant has been sized to the patient's anatomy, thecomputer can create virtual burr zones on the patient's joint surfacesthat represent a typical (e.g., 3-4 mm) offset from the backside of theselected femoral and tibial implant at specific locations of theimplant. These specific locations can include the midpoint (AP) of thedistal cut surface, the vertex of the anterior chamfer and anteriorcuts, along the deepest portion of the implant's trochlear groove, thedistal surface of the tibial implant or other aspects of the tibialcutting guide.

FIGS. 1A-B illustrate generally prepared engagement features (e.g.,102), in accordance with some examples. In an example, for a femoralimplant, after the regions for burring have been set virtually, theNAVIO® system, or other CAS system, can control the cutting action ofthe engagement features (burrs) 102 and allow cutting in the zonesidentified (e.g., the burr zones). For example, a virtual model of theengagement features 102 on the bone 104 can be made and then cuts can bedone as shown in views 100A and 100B. In an example, view 100A includesa view of the bone 104 and engagement features 102 from front view andview 100B includes a view of the bone 104 and engagement features 102from a top view. The engagement features 102 can be cut into the bone104 to provide burr zones for accepting a distal positioning componentof an anterior distal positioning fixture. In an example, a system caninclude two or more engagement features to receive a positioningcomponent or components. For example, four engagement features can beused to receive a distal positioning component of an anterior distalpositioning fixture.

A distal cut can be performed first as this burr zone can be located insuch a manner that it is independent of final implant size selection.The surgeon can make this burr first on the most involved (degenerated)compartment (medial or lateral condyle) and see if adequate bone removalhas been planned in the CAS system. He can also check the ML width ofthe implant selection with the provided size specific instruments. Ifadjustments need to be made, the surgeon can virtually move the implant(e.g., more or less proximal, ML rotation, AP rotation, etc.) in the CASplanning software and the other, remaining burr cuts can be adjustedaccordingly.

Once the surgeon is satisfied with the implant size, the anterior boneresection location can be determined. For example, the location can bewhere the implant will merge with the anterior femur. The location canbe determined with respect to determining if too much notching of theanterior femur will occur. In an example, since the instrument system isnot tied to an IM rod based method, the femoral implant can be rotatedin the sagittal plane to accommodate a different size and still makesure that the posterior positioning of the implant matches the patient'sarticular surfaces.

In an example, the medial-lateral position can be adjusted to provide abest match with the overall femoral width. In another example, theinternal or external rotation can be adjusted so the implant's sulcusmatches the patient's existing Whiteside's line (sulcus/trochleargroove) location. These adjustments can match the implant's trochleargroove with the patient's patella tracking. Once all of the implantpositional adjustments are made, the anterior and sulcus burr zones canbe finished.

FIG. 2 illustrates generally an anterior distal positioning fixture 200in accordance with some examples. The placement of burred cuts (e.g.,engagement features 102 from FIG. 1) can allow for location specificpositioning of a size-specific fixture. With placement of asize-specific Anterior/Distal Positioning Fixture 200 (ADPF), implantsize, proper distal cut depth, AP position, ML position, or properanterior flange width/depth can be confirmed. The confirmation ofimplant positioning or size is not possible at this point in a typicalTKR procedure since significant bone resection has not yet occurred.Position of the ADPF 200 can be fixed with the placement of two or moreheaded screws or pins (e.g., screws 206) into the anterior femur (e.g.,bone 208).

In an example, the ADPF 200 can be placed on the bone 208. A distalpositioning component 202 of the ADPF 200 can be set in the burr zones(e.g., the engagement features of FIG. 1). The distal positioningcomponent 202 can be used to set a position for an anterior positioningblock 204 of the ADPF 200. A distal positioning component can include aspecific example of a secondary positioning component and an anteriorpositioning block can include a specific example of a primarypositioning block. The distal positioning component 202 can be removedafter screws 206 are added to the anterior positioning block 204. In anexample, the burr zones (e.g., engagement features 102 of FIG. 1) aredetermined using a CAS system, then cut into the bone 208. The distalpositioning component 202 can be placed on the bone 208 in a positiondetermined by the CAS system using the engagement features. The distalpositioning component 202 can be used as a guide to properly place theanterior positioning block 204. The anterior positioning block 204 canbe used to place other cutting components to cut the bone 208. Theengagement features or burr zones can be cut into the bone 208 inunobtrusive areas on the bone 208, (e.g., areas that do not affectfunctioning of the bone 208, areas that will be cut again later, areasthat do not cause pain, etc.). Using the distal positioning component202 to guide the anterior positioning block 204 can allow for moreaccurate placement of the anterior positioning block 204 on the bone 208or allow for the burr zones or engagement features to be placed inunobtrusive areas.

FIGS. 3A-D illustrate generally a distal cutting block systems (e.g.,300, 301, or 303) in accordance with some examples. In an example, ageneral cutting block can include a first cutting block or a distalcutting block. In an example, FIG. 3A shows a distal cutting block 304.FIG. 3B shows the distal cutting block 204 in a distal cutting blocksystem 300. In an example, the distal cutting block system 300 of FIG.3B includes an anterior cutting block 306 (e.g., the anteriorpositioning block 204 that was placed in FIG. 2 by the distalpositioning component 202) and a bone 302. The distal cutting block 304can be placed in a position relative to the bone 302 that overlaps witha position for a distal positioning component used to place the anteriorpositioning block 304. For example, a distal positioning component canbe used to place the anterior positioning block 304 and then be removedfollowed by placement of the distal cutting block 306 placed as shown inFIG. 3B. The distal cutting block 306 can be used to make a distal cut,as shown in distal cutting block system 301 in FIG. 3C.

In an example, after a distal positioning component is removed, a distalcutting block 306 can be attached to the remaining anterior positioningblock 304. A distal cut can be made using the distal cutting block 306.The distal cutting block 306 can be removed after the distal cut ismade, as shown in distal cutting block system 303 in FIG. 3D. Theanterior positioning block 304 can remain in place. In an example, asshown in FIGS. 3C and 3D, the distal cutting block 306 can be used tomake a distal cut that removes areas around engagement features on thebone.

FIGS. 4A-B illustrate generally a universal adapter 404 and a 4-in-1cutting block 406 in accordance with some examples. FIG. 4A shows auniversal adapter 404 that can be used in cutting block system 400 inFIG. 4B. The universal adapter 404 can be used to attach the 4-in-1cutting block 406 to the anterior positioning block 402 as shown in FIG.4B. With the use of the universal adapter 404, a standard 4-in-1 cuttingblock (e.g., 4-in-1 cutting block 406) can be attached to the anteriorpositioning block 402. In an example, a femoral peg hole location can bedone prior to attaching the 4-in-1 cutting block 406. In anotherexample, the surgeon can fine tune the ML positioning of the implant atthis point using the cutting block system 400. In an example, theuniversal adapter 404 assists the surgeon in positioning the 4-in-1cutting block 406, while allowing for adjustment in the ML positioningby sliding the 4-in-1 cutting block along a slot in the proximal surfacethat mates with tabs on the universal adapter 404. The 4-in-1 cuttingblock 406 can be attached with screws or pins through peg hole locatorsor wing pinholes. For example, the distal positioning component and the4-in-1 cutting block can re-use holes on the bone for attaching to thebone.

In an example, connecting a component or block to a bone using holes onthe bone or the component can cause positive engagement of the componentor block with the bone. This can improve accuracy of subsequent bonecuts. For example, a component or block can be loosely fitted to a boneand then tightened to an accurate engagement position by screwing orpinning the component or block to the bone.

The anterior positioning block 402 and the universal adapter 404 can beremoved after the 4-in-1 cutting block 406 is secure or attached. In anexample, the universal adapter 404 or 4-in-1 cutting block 406 can bepositioned relative to the bone in positions that overlap a portion ofone or more of the areas previously occupied by the distal cutting blockor the distal positioning component. For example, two or more of thedistal cutting block, distal positioning component, universal adapter,or 4-in-1 cutting block 406 can attach to a same face of the anteriorpositioning block 402.

In another example, the femur can be prepared using navigated holes thatcan result in further substantial time-savings. By using the navigatedholes, steps can be eliminated from a standard procedure, including useof the traditional IM distal cut apparatus, use of the femoral sizerapparatus, or determination of the cutting position blocks location.

In yet another example, the methods and systems described can be used ina minimally invasive surgery (MIS) total knee replacement (TKR). Forexample, a positioning block or positioning component can include amedial or lateral positioning block or positioning component. Apositioning block or component can be designed for use in a MIS TKR orcan be used without modification from those used for a typical TKR. TheMIS TKR can include a positioning block or component used to avoidmuscle (e.g., muscle sparing) or when using minimal arthrotomy length.In non-typical, non-MIS, procedures, devices, components, blocks, etc.,described herein can be modified for use in special circumstances. Forexample, if everted patella or typical arthrotomy length are not presentin a procedure, one or more of the components, blocks, devices, cuts,etc., can be modified to aid in surgery.

Various components, blocks, devices, instruments, etc., described hereincan be re-used or be disposable after one use. For example, one or moreof an anterior positioning block, distal positioning component, distalcutting block, 4-in-1 cutting block, universal adapter, tibial cuttingblock, tibial plate trial, or navigation positioner can be disposableand used only once, or can be re-used. In an example, one or more of thecomponents, blocks, etc., described herein can include a material thatallows for deformation. For example, a component or block can be madewith a spring-like material (e.g., rubber, plastic, etc.) that allows apositive engagement with a bone via bending displacement. In an example,a component or block can be manufactured or fabricated as a single,unitary component or block. In another example, a component or block canbe manufactured or fabricated in parts (e.g., two parts combined to makea component or block). Manufacturing or fabricating a tibial componentin parts can facilitate a positive or locking connection to a bone.Manufacturing or fabricating can include traditional manufacturing, 3Dprinting, sculpting, etc.

In an example, additional operating room (OR) time that might be addedby the use of a navigation procedure can be made up by use of the NAVIO®optimized instruments. The methods and systems described herein caninclude a “Patient Specific” knee implantation without usingpre-procedure imaging or patient specific cutting guides or patientspecific implants.

FIGS. 5A-B illustrate generally a tibial cutting block (e.g., 504A or504B) in accordance with some examples. In an example, tibialpreparations can be done in a similar manner to the methods and usingthe systems as described above for a femur (or other bone). For tibialpreparations, an implant can be pre-positioned using the NAVIO® Softwareduring a planning phase. Using the NAVIO® software, a cutting plane canbe determined using a best-fit implant size and position.

In an example, the NAVIO® system can determine simple burred regions(e.g., three (3) or four (4) burr regions or zones-creating engagementfeatures on the tibia) of the bone 502 that provide a correct posteriorslope angle for the location of a tibial cutting block (e.g., 504A or504B). A single left (L) or right (R) cutter can be used for any sizeimplants. As shown in FIG. 5A, tibial cutting system 500 can include thebone 502 (e.g., tibia) and the tibial cutting block 504A. Other versionsof a tibial cutting block can be used (e.g., 504B shown in FIG. 5B). Inanother example, an integrated positioning and cutting guide block canbe used for positioning and location.

In an example, after the positional burr cuts have been made to createengagement features, the tibial cutting block (e.g., 504A or 504B) canbe placed in an unambiguous manner onto the tibia. The tibial cuttingblock (e.g., 504A or 504B) can be pinned in place with headed ornon-headed pins to secure the guide during the subsequent bone-cuttingoperation. After a tibial cut has been made using the tibial cuttingblock (e.g., 504A or 504B), a tibial trial plate or an appropriatepolyethylene insert trials of an appropriate thickness can be used tocheck for an appropriate knee joint extension or flexion gap. In anexample, the tibial cutting block (e.g., 504A or 504B) can be removedprior to installing the tibial trial plate or polyethylene insert trial.In an example, a change to a slope angle can be done by repositioningthe system. The system can be reused for a re-cutting procedure or aspecial re-cutting tibial cutting block can be used to increase thecutting depth or change the posterior slope of the tibial cut.

The implant geometry, specifically the femoral and polyethylene insertimplant articulating surfaces, can be known to the CAS system via adatabase, and the ML rotation or AP rotation of the tibial components(tibial plate or polyethylene insert) can be aligned on the resectedtibia. For example, the alignment can include a best fit positionrelative to the femoral implant so as not to create a mismatch of thefemoral or tibial components during ambulation.

During extension of the knee, it is particularly important to align thearticulating surface of the femoral and polyethylene inserts properly.Improper alignment can result in asymmetrical loading of the medial andlateral compartments, which can cause patient discomfort, sudden shiftsin the knee position, or rapid rates of polyethylene wear. Asymmetricalloading can also cause the potential for cemented component looseningfrom the bone.

FIGS. 6A-B illustrate generally a properly placed femoral implant (e.g.,600A or 600B) in accordance with some examples. As shown in FIG. 6A, aML cross-section, and as shown in FIG. 6B, an AP view, of a typicalfemoral implant in extension can be ideally located on the polyethyleneinsert. FIGS. 6A and 6B demonstrate a desired relationship between thefemoral and tibial components when the leg is in the weight-bearingextension position.

FIG. 7 illustrates generally improperly placed femoral implants (e.g.,700A, 700B, 700C, 700D, or 700E) in accordance with some examples.Various examples in FIG. 7 show that any mal-rotation of the relativeimplant positions can cause localized areas of increased loading of thepolyethylene insert and resultant abnormal rotation (either external orinternal) of the tibial bone relative to the femur for the patientduring ambulation, resulting in abnormal wear of the polyethylene insertand pain or discomfort for the patient.

FIG. 8 illustrates generally a tibial plate trial 804 and navigationpositioner 806 in accordance with some examples. To aid in minimizingthe chance for tibial plate positioning errors, using a navigationsystem, a navigated positioner 806 can be attached to the tibial platetrial 804 prior to the punching of the tibia 802 for tibial keel in atibial implant placement system 800. Pins 808 can be used to attach thetibial plate trial 804 to the tibia 802. In an example, the pinspreviously placed to secure the tibial cut guide can be used to minimizethe chance for tibial plate positioning errors. For example, thenavigated burr zones have been used to locate the cutting guide and todetermine the pin position, and can be used in conjunction with aguiding device that interfaces with both the tibial plate trial andthese pins. This can set ML rotational orientations of the tibial platetrial per the navigation plan. The AP location can be confirmed byplacing the stylus onto a known reference on the tibial plate, where thenull point of the tibial (e.g., polyethylene) insert location can bepositioned to line up with the extension position of the femoralimplant.

In yet another example, the most anterior burr zones can be madeslightly deeper into the tibial plateau. This can allow the burr zonesto still be visible after the tibial cut has been made. The burr zonescan also be used to identify the anterior edge of the trial tibial platefor AP location. This, in combination with the ML or rotationalplacement dictated by the pin placement, can locate the trial tibialplate in an optimal position on the tibia and relative to the previouslylocated femoral trial on the femur. As a result, the implants, andconsequently the femur and tibia, can be in ideal positions to oneanother to maximize patient comfort and to maximize functioning of theknee and the implants.

In the examples described above and illustrated in FIGS. 1A-5B, some ofthe positioning components (e.g., anterior positioning block or distalpositioning component) are discussed as involving multiple matingcomponents that couple together during use to form a completepositioning component or guide. In some examples, a unitary positioningcomponent is used that can be fabricated from deformable (e.g.,spring-like) materials that will snap into engagement features machinedinto the bone. Applications of the discussed instrumentation andtechniques may be modified in certain ways, such as unitary positioningcomponents or multi-part positioning components, depending upon therequirements of the particular procedure or target joint (e.g., elbow,hip, shoulder, etc . . . ).

The examples described above may reference positioning components or cutguides by particular names that may indicate how the particular piece ofinstrumentation is used in the example procedure, such as the anteriorpositioning block). These specific names are used solely to provideadditional clarity within the described example procedure. Thepositioning component concepts and related tools for creation ofengagement features discussed are applicable to other proceduresinvolving resection of bone or soft tissue within various anatomicallocations.

FIG. 9 is a block diagram that illustrates an example of a block diagramof a machine in the form of a computer system 900 within whichinstructions, for causing the computer system to perform any one or moreof the methods discussed herein, can be executed. In variousembodiments, the machine can operate as a standalone device or can beconnected (e.g., networked) to other machines. In a networkeddeployment, the machine can operate in the capacity of a server or aclient machine in server-client network environment, or as a peermachine in a peer-to-peer (or distributed) network environment. Themachine can be a personal computer (PC), a tablet PC, a set-top box(STB), a PDA, a cellular telephone, a web appliance, a network router,switch or bridge, or any machine capable of executing instructions(sequential or otherwise) that specify actions to be taken by thatmachine. Further, while only a single machine is illustrated, the term“machine” shall also be taken to include any collection of machines thatindividually or jointly execute a set (or multiple sets) of instructionsto perform any one or more of the methodologies discussed herein.

The example computer system 900 includes a processor 902 (such as acentral processing unit (CPU), a graphics processing unit (GPU), orboth), a main memory 904 and a static memory 906, which communicate witheach other via a bus 908. The computer system 900 can further include avideo display unit 910 (such as a liquid crystal display (LCD) or acathode ray tube (CRT)), an alpha-numeric input device 912 (such as akeyboard), a user interface (UI) navigation device (or cursor controldevice) 914 (such as a mouse), a disk drive unit 916, a signalgeneration device 918 (e.g., a speaker) and a network interface device920.

The disk drive unit 916 includes a machine-readable storage medium 922on which is stored one or more sets of instructions and data structures(e.g., software) 924 embodying or used by any one or more of the methodsor functions described herein. The instructions 924 can also reside,completely or at least partially, within the main memory 904, staticmemory 906, or within the processor 902 during execution thereof by thecomputer system 900, the main memory 904 and the processor 902 alsoconstituting machine-readable media. In an example, the instructions 924stored in the machine-readable storage medium 922 include instructionscausing the computer system 900 to determine a patient-specific model ofthe bone and using a computer controlled cutting instrument 930, preparean engagement feature in the bone using the patient-specific model. Theinstructions 924 can also store the instructions 924 that cause thecomputer system 900 to create a virtual model to be used to prepare anengagement feature on a bone. The machine-readable storage medium 922can further store the instructions 924 that cause the computer system900 to operate a computer aided surgery (CAS) system.

While the machine-readable medium 922 is shown in an example embodimentto be a single medium, the term “machine-readable medium” can include asingle medium or multiple media (e.g., a centralized or distributeddatabase, and/or associated caches and servers) that store the one ormore instructions or data structures. The term “machine-readable storagemedium” shall also be taken to include any tangible medium that iscapable of storing, encoding or carrying instructions for execution bythe machine and that cause the machine to perform any one or more of themethods of the present invention, or that is capable of storing,encoding or carrying data structures used by or associated with suchinstructions. The term “machine-readable storage medium” shallaccordingly be taken to include, but not be limited to, solid-statememories, and optical and magnetic media. Specific examples ofmachine-readable media include non-volatile memory, including by way ofexample, semiconductor memory devices (e.g., erasable programmableread-only memory (EPROM), electrically erasable programmable read-onlymemory (EEPROM)) and flash memory devices; magnetic disks such asinternal hard disks and removable disks; magneto-optical disks; andCD-ROM and DVD-ROM disks. A “machine-readable storage medium” shall alsoinclude devices that can be interpreted as transitory, such as registermemory, processor cache, and RAM, among others. The definitions providedherein of machine-readable medium and machine-readable storage mediumare applicable even if the machine-readable medium is furthercharacterized as being “non-transitory.” For example, any addition of“non-transitory,” such as non-transitory machine-readable storagemedium, is intended to continue to encompass register memory, processorcache and RAM, among other memory devices.

In various examples, the instructions 924 can further be transmitted orreceived over a communications network 926 using a transmission medium.The instructions 924 can be transmitted using the network interfacedevice 920 and any one of a number of well-known transfer protocols(e.g., HTTP). Examples of communication networks include a LAN, a WAN,the Internet, mobile telephone networks, plain old telephone (POTS)networks, and wireless data networks (e.g., Wi-Fi and WiMAX networks).The term “transmission medium” shall be taken to include any intangiblemedium that is capable of storing, encoding or carrying instructions forexecution by the machine, and includes digital or analog communicationssignals or other intangible media to facilitate communication of suchsoftware.

FIG. 10 is a flowchart showing a method 1000 for operating a system foruse in orthopedic surgery on a bone in accordance with some examples.The method 1000 can include an operation 1002 to determine apatient-specific model of a bone and an operation 1004 to use a computercontrolled cutting instrument to prepare an engagement feature in thebone using the patient-specific model. The method 1000 can include anoperation 1006 to guide an anterior positioning block (e.g., anteriorpositioning block 204) to a predetermined position on the bone using adistal positioning component (e.g., distal positioning component 202)and the prepared engagement feature (e.g., engagement features 102). Inan example, the distal positioning component can be attached to theanterior positioning block. The method 1000 can include removing thedistal positioning component after the anterior positioning block isattached to the target bone.

The method 1000 can include an operation 1008 to affix a distal cuttingblock (e.g., distal cutting block 304) to the anterior positioningblock. In an example, the distal cutting block can be affixed to theanterior positioning block after the distal positioning component isremoved. The positions for affixing the distal cutting block and thedistal positioning component can be overlapping. For example, when thedistal cutting block and distal positioning component are affixed inoverlapping positions, only one can be attached or affixed to theanterior positioning block at a time.

The method 1000 can include an operation 1010 to cut the bone along aguide plane of the distal cutting block. In an example, the method 1000includes removing the distal cutting block after cutting the bone alongthe guide plane, attaching a 4-in-1 cutting block (e.g., 4-in-1 cuttingblock 406) to the anterior positioning block using a universal adapter(e.g., universal adapter 404), and cutting the bone along a guide planeof the 4-in-1 cutting block.

FIG. 11 is a flowchart showing a method 1100 for operating a system foruse in orthopedic surgery on a bone in accordance with some examples.The method 1100 can include an operation 1102 to determine apatient-specific model of a bone and an operation 1104 to use a computercontrolled cutting instrument to prepare an engagement feature in thebone using the patient-specific model. The method 1100 can include anoperation 1106 to attach a tibial cutting block (e.g., tibial cuttingblock 504A or 504B) to the bone in a predetermined position using theprepared engagement feature. The method 1100 can include an operation1108 to cut the bone along a guide plane of the tibial cutting block.The method 1100 can be used to place a tibial trial plate and re-cut thebone if needed. The tibial cutting block can be re-used to re-cut thebone or a new re-cutting tibial block can be used to re-cut the bone. Inan example, after cutting and, if necessary, re-cutting, a polyethyleneinsert can be attached to the bone. In another example, a navigatedpositioner (e.g., navigated positioner 806) can be attached to a tibialtrial plate (e.g., tibial trial plate 804) to determine an appropriateknee joint extension or flexion gap.

VARIOUS NOTES & EXAMPLES

Each of these non-limiting examples can stand on its own, or can becombined in various permutations or combinations with one or more of theother examples.

Example 1 includes the subject matter embodied by an orthopedic surgicaldevice for use in operating on a target bone comprising: a primarypositioning block, a secondary positioning component removably coupledto the primary positioning block, the secondary positioning componentconfigured to: engage a prepared engagement feature machined into thetarget bone, and guide the primary positioning block to a predeterminedposition on a target bone, and a first cutting block configured to:removably couple to the primary positioning block, and guide a cuttingtool to cut the target bone.

In Example 2, the subject matter of Example 1 can optionally includewherein the prepared engagement feature is created using a virtualmodel.

In Example 3, the subject matter of one or any combination of Examples1-2 can optionally include wherein the virtual model includes apatient-specific virtual model of the target bone.

In Example 4, the subject matter of one or any combination of Examples1-3 can optionally include further comprising a 4-in-1 cutting blockremovably coupled to the primary positioning block.

In Example 5, the subject matter of one or any combination of Examples1-4 can optionally include wherein the 4-in-1 cutting block is coupledto the primary positioning block after the secondary positioningcomponent is removed.

In Example 6, the subject matter of one or any combination of Examples1-5 can optionally include wherein the 4-in-1 cutting block isconfigured to removably couple to the primary positioning block in aconfiguration at least partially overlapping a position of the secondarypositioning component or the first cutting block.

In Example 7, the subject matter of one or any combination of Examples1-6 can optionally include wherein the 4-in-1 cutting block is removablycoupled to the primary positioning block using a universal adapter.

In Example 8, the subject matter of one or any combination of Examples1-7 can optionally include wherein the 4-in-1 cutting block is furtherconfigured to guide a plurality of cuts.

In Example 9, the subject matter of one or any combination of Examples1-8 can optionally include wherein the 4-in-1 cutting block isconfigured to guide the plurality of cuts when the primary positioningblock and the universal adapter are removed.

In Example 10, the subject matter of one or any combination of Examples1-9 can optionally include wherein the secondary positioning componentand the first cutting block are configured to removably couple to theanterior positioning block in partially overlapping positions.

In Example 11, the subject matter of one or any combination of Examples1-10 can optionally include wherein the secondary positioning component,the first cutting block, and the primary positioning block are notpatient-specific.

In Example 12, the subject matter of one or any combination of Examples1-11 can optionally include wherein the primary positioning block is ananterior positioning block, the secondary positioning component is adistal positioning component, and the first cutting block is a distalcutting block.

Example 13 includes the subject matter embodied by a system forpreparing a bone in a joint for an implant, the system comprising: acomputer controlled cutting instrument configured to prepare anengagement feature in the bone, a positioning fixture, configured toengage the prepared engagement feature, the positioning fixturecomprising: a primary positioning block, and a secondary positioningcomponent removably coupled to the primary positioning block, and afirst cutting block configured to: removably couple to the primarypositioning block, and guide a cutting tool to cut the bone.

In Example 14, the subject matter of Example 13 can optionally include a4-in-1 cutting block configured to: removably couple to the primarypositioning block using a universal adapter, and guide a second cuttingtool to cut the bone.

In Example 15, the subject matter of one or any combination of Examples13-14 can optionally include wherein the prepared engagement feature iscreated using a virtual model.

In Example 16, the subject matter of one or any combination of Examples13-15 can optionally include wherein the bone is a femur.

In Example 17, the subject matter of one or any combination of Examples13-16 can optionally include wherein the computer controlled cuttinginstrument is controlled by a computer aided surgery (CAS) system.

In Example 18, the subject matter of one or any combination of Examples13-17 can optionally include wherein the primary positioning block is ananterior positioning block, the secondary positioning component is adistal positioning component, and the first cutting block is a distalcutting block.

Example 19 includes the subject matter embodied by a method foroperating a system for use in orthopedic surgery on a bone, the methodcomprising: determining a patient-specific model of the bone, using acomputer controlled cutting instrument to prepare an engagement featurein the bone using the patient-specific model, guiding a primarypositioning block to a predetermined position on the bone using asecondary positioning component and the prepared engagement feature,affixing a first cutting block to the primary positioning block, andcutting the bone along a guide plane of the first cutting block.

In Example 20, the subject matter of Example 19 can optionally includewherein the secondary positioning component is attached to the primarypositioning block and further comprising removing the secondarypositioning component after the primary positioning block is attached tothe target bone.

In Example 21, the subject matter of one or any combination of Examples19-20 can optionally include wherein the first cutting block is affixedto the primary positioning block after the secondary positioningcomponent is removed.

In Example 22, the subject matter of one or any combination of Examples19-21 can optionally include removing the first cutting block aftercutting the bone along the guide plane, attaching a 4-in-1 cutting blockto the primary positioning block using a universal adapter, and cuttingthe bone along a guide plane of the 4-in-1 cutting block.

In Example 23, the subject matter of one or any combination of Examples19-22 can optionally include wherein the primary positioning block is ananterior positioning block, the secondary positioning component is adistal positioning component, and the first cutting block is a distalcutting block.

In Example 24, the subject matter of one or any combination of Examples1-23 can optionally include wherein the primary positioning block iscreated from a virtual model.

In Example 25, the subject matter of one or any combination of Examples1-24 can optionally include wherein the secondary positioning componentis created from a virtual model.

In Example 26, the subject matter of one or any combination of Examples1-25 can optionally include wherein the first cutting block is createdfrom a virtual model.

Example 27 includes the subject matter embodied by a method foroperating a system for use in an orthopedic surgery on a bone, themethod comprising: determining a patient-specific model of the bone,modeling virtual engagement features on the patient-specific model ofthe bone to fit an anterior/distal positioning fixture, theanterior/distal positioning fixture including an anterior positioningblock and a distal positioning component, making engagement feature cutson the bone using the virtual engagement features, affixing the physicalanterior/distal positioning fixture to the bone using the engagementfeature cuts, removing the distal positioning component from the bone,attaching a distal cutting block to the anterior positioning block,making a distal cut on the bone using the distal cutting block, removingthe distal cutting block from anterior positioning block, attaching a4-in-1 cutting block to the bone using a universal adapter and theanterior positioning block, removing the anterior positioning block andthe universal adapter, making a plurality of cuts on the bone using the4-in-1 cutting block, or attaching an implant aligned with the pluralityof cuts.

Example 28 includes the subject matter embodied by a method foroperating a system for use in an orthopedic surgery on a bone, themethod comprising: determining a patient-specific model of the bone,modeling virtual engagement features on the patient-specific model ofthe bone to fit a tibial cutting block, making engagement feature cutson the bone using the virtual engagement features, affixing a tibialcutting block to the bone with screws or pins using the engagementfeature cuts, making a tibial cut on the bone using the tibial cuttingblock, removing the tibial cutting block, placing a tibial plate on thebone, attaching a navigated positioner to the tibial plate trial,determining if a re-cut is needed using the physical tibial plate on thebone, or attaching a polyethylene insert to the bone.

Example 29 includes the subject matter embodied by a system comprisingcomputer assisted surgery software, an anterior distal positioningfixture including a distal positioning portion and an anteriorpositioning block, a distal cutting block, a universal adapter, or a4-in-1 cutting block.

The above detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments. These embodimentsare also referred to herein as “examples.” Such examples can includeelements in addition to those shown or described. However, the presentinventors also contemplate examples in which only those elements shownor described are provided. Moreover, the present inventors alsocontemplate examples using any combination or permutation of thoseelements shown or described (or one or more aspects thereof), eitherwith respect to a particular example (or one or more aspects thereof),or with respect to other examples (or one or more aspects thereof) shownor described herein.

In the event of inconsistent usages between this document and anydocuments so incorporated by reference, the usage in this documentcontrols.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In this document, the terms “including” and “inwhich” are used as the plain-English equivalents of the respective terms“comprising” and “wherein.” Also, in the following claims, the terms“including” and “comprising” are open-ended, that is, a system, device,article, composition, formulation, or process that includes elements inaddition to those listed after such a term in a claim are still deemedto fall within the scope of that claim. Moreover, in the followingclaims, the terms “first,” “second,” and “third,” etc. are used merelyas labels, and are not intended to impose numerical requirements ontheir objects.

Method examples described herein can be machine or computer-implementedat least in part. Some examples can include a computer-readable mediumor machine-readable medium encoded with instructions operable toconfigure an electronic device to perform methods as described in theabove examples. An implementation of such methods can include code, suchas microcode, assembly language code, a higher-level language code, orthe like. Such code can include computer readable instructions forperforming various methods. The code can form portions of computerprogram products. Further, in an example, the code can be tangiblystored on one or more volatile, non-transitory, or non-volatile tangiblecomputer-readable media, such as during execution or at other times.Examples of these tangible computer-readable media can include, but arenot limited to, hard disks, removable magnetic disks, removable opticaldisks (e.g., compact disks and digital video disks), magnetic cassettes,memory cards or sticks, random access memories (RAMs), read onlymemories (ROMs), and the like.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) can be used in combination with each other. Otherembodiments can be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is provided to complywith 37 C.F.R. § 1.72(b), to allow the reader to quickly ascertain thenature of the technical disclosure. It is submitted with theunderstanding that it will not be used to interpret or limit the scopeor meaning of the claims. Also, in the above Detailed Description,various features can be grouped together to streamline the disclosure.This should not be interpreted as intending that an unclaimed disclosedfeature is essential to any claim. Rather, inventive subject matter canlie in less than all features of a particular disclosed embodiment.Thus, the following claims are hereby incorporated into the DetailedDescription as examples or embodiments, with each claim standing on itsown as a separate embodiment, and it is contemplated that suchembodiments can be combined with each other in various combinations orpermutations.

What is claimed is:
 1. A system for preparing a bone in a joint for animplant, the system comprising: a computer controlled cutting instrumentconfigured to prepare an engagement feature in the bone, wherein theengagement feature comprises a cut into the bone positioned based upon asize of the bone and corresponding to a computer-identified location ofa burr zone; a positioning fixture configured to engage the preparedengagement feature, the positioning fixture comprising: at least onepositioning component configured to be set into position within theengagement feature, a primary positioning block configured to bepositioned relative to the at least one positioning component and to beaffixed to the bone using removable fasteners when in position, andwherein the at least one positioning component comprises a secondarypositioning component removably coupled to the primary positioningblock; and a first cutting block configured to: removably couple to theprimary positioning block, and guide a cutting tool to cut the bone. 2.The system of claim 1, wherein the computer-identified location of theburr zone for the prepared engagement feature is identified using avirtual model.
 3. The system of claim 1, wherein the bone is a femur. 4.The system of claim 1, wherein the computer controlled cuttinginstrument is configured to be controlled by a computer aided surgery(CAS) system.
 5. The system of claim 4, wherein the CAS system isconfigured to identify the location of the burr zone for placement ofthe engagement feature.
 6. The system of claim 1, wherein the at leastone positioning component comprises a distal positioning componentconfigured to be positioned within the engagement feature for alignmentof the primary positioning block to the bone, wherein the distalpositioning component is positionable at a distal end of the bone. 7.The system of claim 6, wherein the primary positioning block comprisesan anterior positioning block configured to removably couple to thedistal positioning component, wherein the anterior positioning block ispositionable at an anterior surface of the bone.
 8. The system of claim1, wherein the first cutting block comprises a distal cutting blockconfigured to guide the cutting tool to cut a distal cut in the bone,wherein the distal cutting block is positionable at a distal end of thebone.
 9. A system for preparing a bone in a joint for an implant, thesystem comprising: a computer controlled cutting instrument configuredto prepare a plurality of engagement features in the bone, wherein eachof the plurality of engagement features comprises a cut into the bonepositioned based upon a size of the bone and corresponding to acomputer-identified location of a burr zone; a positioning fixtureconfigured to engage the plurality of engagement features, thepositioning fixture comprising: at least one positioning componentconfigured to be set into position within the plurality of engagementfeatures, a primary positioning block configured to be positionedrelative to the at least one positioning component and to be affixed tothe bone using removable fasteners when in position, and wherein the atleast one positioning component comprises a secondary positioningcomponent removably coupled to the primary positioning block; and afirst cutting block configured to: removably couple to the primarypositioning block, and guide a cutting tool to cut the bone.
 10. Thesystem of claim 9, wherein the computer-identified location of the burrzone for the prepared engagement feature is identified using a virtualmodel.
 11. The system of claim 9, wherein the computer controlledcutting instrument is configured to be controlled by a computer aidedsurgery (CAS) system.
 12. The system of claim 11, wherein the CAS systemis configured to identify the location of the burr zone for placement ofa corresponding engagement feature.
 13. The system of claim 9, whereinthe at least one positioning component comprises a distal positioningcomponent configured to be positioned within the plurality of engagementfeatures for alignment of the primary positioning block to the bone,wherein the distal positioning component is positionable at a distal endof the bone.
 14. The system of claim 13, wherein the primary positioningblock comprises an anterior positioning block configured to removablycouple to the distal positioning component, wherein the anteriorpositioning block is positionable at an anterior surface of the bone.15. The system of claim 9, wherein the first cutting block comprises adistal cutting block configured to guide the cutting tool to cut adistal cut in the bone, wherein the distal cutting block is positionableat a distal end of the bone.
 16. The system of claim 9, wherein theremovable fasteners comprise at least one of screws and pins.
 17. Asystem for preparing a bone in a joint for an implant, the systemcomprising: a computer controlled cutting instrument configured toprepare a plurality of engagement features in the bone, wherein each ofthe plurality of engagement features comprises a cut into the bonepositioned based upon a size of the bone and corresponding to acomputer-identified location of a pin hole, wherein thecomputer-identified location of the pin hole for each of the pluralityof engagement features is identified using a virtual model, wherein thecomputer controlled cutting instrument is configured to be controlled bya computer aided surgery (CAS) system, wherein the CAS system isconfigured to identify the location of the pin hole for placement of acorresponding engagement feature; a positioning fixture configured toengage the plurality of engagement features, the positioning fixturecomprising: at least one positioning component configured to be set intoposition within the plurality of engagement features, a primarypositioning block configured to be positioned relative to the at leastone positioning component and to be affixed to the bone using removablefasteners when in position, and wherein the at least one positioningcomponent comprises a secondary positioning component removably coupledto the primary positioning block; and a first cutting block configuredto: removably couple to the primary positioning block, and guide acutting tool to cut the bone.